A great number of aircraft landing accidents are associated with improper landing gear configuration during landing. For example, one of the largest sources of insurance claims for retractable gear aircraft is gear up landings when an aircraft lands on a runway with the landing gear retracted, causing the aircraft to contact the ground initially with its belly, propeller(s), engine(s), and wing(s). Even if the landing is successfully completed, and injury or loss of life is avoided, the accident naturally results in extensive damage to the aircraft. Another type of landing gear status accident may involve amphibians landing on water. Amphibians are typically equipped to land on water or land, and thus have landing gear that can be extended below the aircraft's pontoon structures, or “floats”. However, if the landing gear is extended when a amphibian is landing on water, the aircraft will typically flip forward into the water upon the landing gear's impact with the water, potentially resulting in damage to the aircraft and injury to the crew and passengers. While amphibian pilots may be particularly susceptible to committing gear status errors, due to the difference in the proper gear status for any landing surfaces, any pilot may be subject to this lapse.
Prior landing gear warning systems typically rely on outside variables such as flap position and/or throttle speed. However, experience has shown that it is very easy for the pilot to operate the aircraft in a manner that renders these systems ineffective. Various situations and circumstances may cause a pilot to attempt a landing while these variables are not in the typical configuration for landing. For example, using a high throttle speed when landing, such as under gusty conditions or when approaching at high speed, can leave the pilot unprotected. Since the aircraft variable is not in the typical landing state, no gear warning is issued, and the error is not brought to the pilot's attention. In addition, false warnings can be initiated when the pilot is not trying to land. Improper landing gear configurations generally happen when distractions occur in the cockpit. Further, the use of headsets has made it more difficult to hear and recognize the cockpit warnings. There have also been many instances of pilots misinterpreting the gear warning horn, or ignoring it completely, resulting in improper gear configuration during landing. It would be desirable to provide a gear status-warning indicator based on variables that are highly, if not completely, correlated with the typical landing protocol.
Previous systems have tried to provide gear status-warning indicators based on variables correlating with typical landing protocol. U.S. Pat. No. 4,516,124 describes a pilot warning system for amphibious aircraft with retractable landing gear which includes a prompting device for warning the pilot that the aircraft is in transition between a landing speed and a cruising speed. The pilot must then take action and press a button indicating, prior to landing, whether the landing is to be on land or on water. An indicator tells the pilot if the retractable landing gear is in a position corresponding to the designated landing surface. If a water landing is proposed and the landing gear is retracted, operations proceed normally. If the landing gear is sensed to be extended, the pilot is alerted to this situation. Similarly, if a landing on a runway is proposed, the pilot is alerted if the landing gear is not extended.
U.S. Pat. No. 6,008,742 provides for a transducer unit to sense ground presence. A signal is continuously radiated downward from the transducer. When the signal strikes a surface, a portion of the radiated energy is reflected back to the transducer. A receiving device reacts to this reflected signal. An electronic module analyzes the electronic signals produced by the transducer unit, and also determines if the aircraft landing gear is retracted or extended. When the electronic module determines that the aircraft is in close proximity to the ground, approximately 100 ft. to 200 ft, it then determines if the landing gear is retracted or extended. This is accomplished by monitoring the status of the landing gear down indicator light. If it is determined that the aircraft is close to the ground, and the landing gear is still retracted, it produces a warning to the pilot. The warnings continue until the pilot either extends the landing gear, or climbs the aircraft more than 200 ft. above ground level.
U.S. Pat. No. 5,745,053 provides for a landing gear warning system for aircraft. The landing gear warning system consists of a landing gear sensor for generating a signal representative of the position of the landing gear, an aircraft positioning system for generating a signal representative of the aircraft's latitude, longitude, and elevation, a pilot warning device, and a computer system coupled to the landing gear sensor, the aircraft positioning system, and the pilot warning device. The computer system has a database that contains the longitude and latitude, and elevation of a number of runways, receives a signal representative of the aircraft's latitude, longitude, and elevation, receives a signal representative of the position of the landing gear member, and generates a pilot warning signal if the aircraft's elevation is less than a predetermined value above the elevation of the closest runway in the database to the aircraft and the signal representative of the position of the landing gear indicates that the retractable landing gear is retracted.
It will be appreciated that the '124 patent requires the pilot to take action first checking the landing gear status upon a speed indication of a possible landing and second checking the type of surface the aircraft is landing on. Further, studies have shown that pilots will choose the incorrect landing gear configuration 2-3 times out of 1000. The chance of these occurrences is increased where there is water located near the runway and the pilot has indecision about which surface he/she wants to land upon. The '742 and '053 patents may serve to inform the pilot of the altitude of the aircraft and the status of the landing gear, however, these pilot warning systems do not inform the pilot whether the landing gear should be retracted or deployed depending on the surface on which the aircraft will be landing.
Therefore, it would be desirable to provide an improved landing gear system to prevent or reduce the incidence of pilot error associated with incorrect gear status landings, requiring no affirmative pilot input, and giving warnings or indications consistent with the landing scenario.